The ultrastructure of the liver in thyroid-fed rats

Summary

Rats were fed on a 25% casein diet or the same diet supplemented with desiccated thyroid. The rats were killed after 16 days. Histological sections of the livers of the control rats show coarse, basophilic inclusions and abundance of glycogen in the cytoplasm. In the thyroid-fed rats there is a diffuse, cytoplasmic basophilia with basophilic rods and no or almost no glycogen. Under the electron microscope large areas of glycogen are to be seen in the cytoplasm of the control animals. Mitochondria and rough-surfaced endoplasmic membranes, often in large stacks, are found together. The liver cells of the thyroid-fed rats have little or no glycogen in their cytoplasm. Mitochondria, endoplasmic reticulum, and free ribosomes and polysomes are evenly distributed all over the cytoplasm. There seems to be an increase in the ratio of free to membrane-bound ribosomes and polysomes in the thyroid-fed rats. The possible significance of this observation in relation to RNA synthesis is discussed.